Thermal transfer printing has displaced impact printing in many applications due to advantages such as relatively low noise levels during the printing operation. Thermal transfer printing is widely used in special applications such as in the printing of machine readable bar codes and magnetic alpha-numeric characters. The thermal transfer process provides great flexibility in generating images and allows for broad variations in style, size and color of the printed image. Representative documentation in the area of thermal printing includes the following patents:
U.S. Pat. No. 3,663,278, issued to J. H. Blose et al. on May 16, 1972; PA1 U.S. Pat. No. 4,315,643, issued to Y. Tokunaga et al. on Feb. 16, 1982; PA1 U.S. Pat. No. 4,403,224, issued to R. C. Winowski on Sep. 6, 1983; PA1 U.S. Pat. No. 4,463,034, issued to Y. Tokunaga et al. on Jul. 31, 1984; PA1 U.S. Pat. No. 4,628,000, issued to S. G. Talvalkar et al. on Dec. 9, 1986; PA1 U.S. Pat. No. 4,687,701, issued to K. Knirsch et al. on Aug. 18, 1987; PA1 U.S. Pat. No. 4,707,395, issued to S. Ueyama et al., on Nov. 17, 1987; PA1 U.S. Pat. No. 4,777,079, issued to M. Nagamoto, et al. on Oct. 11, 1988; PA1 U.S. Pat. No. 4,778,729, issued to A. Mizobuchi on Oct. 18, 1988; PA1 U.S. Pat. No. 4,923,749, issued to Talvalkar on May 8, 1990; PA1 U.S. Pat. No. 4,975,332, issued to Shini et al. on Dec. 4, 1990; PA1 U.S. Pat. No. 4,983,446, issued to Taniguchi et al. on Jan. 8, 1991; PA1 U.S. Pat. No. 4,988,563, issued to Wehr on Jan. 29, 1991; PA1 U.S. Pat. Nos. 5,128,308 and 5,248,652, issued to Talvalkar; and PA1 U.S. Pat. No. 5,240,781, issued to Obatta et al. PA1 a) the thermal transfer ribbon; PA1 b) the source of the thermal transfer ribbon; PA1 c) how to install the thermal transfer ribbon in a thermal transfer printer; PA1 d) how to use the thermal transfer ribbon in a thermal transfer printer; and/or PA1 e) how to replace the thermal transfer ribbon when installed in a thermal transfer printer.
Most thermal transfer ribbons employ a synthetic resin as a substrate. Polyethylene terephthalate (PET) polyester is commonly used. The functional layer which transfers ink, also referred to as the thermal transfer layer, is deposited on one side of the substrate and a protective silicone backcoat is typically deposited on the other side of the polyethylene terephthalate substrate to simplify passage under a thermal print head.
Leaders which are stiffer than the thermal transfer ribbons are attached to the beginning of the ribbon to simplify installation into the thermal transfer printers. With the use of a leader, the operator who threads the thermal transfer ribbon into the thermal transfer printer need not touch the ink layer. This helps keep the operator and the equipment clean and protects the ink layer at the beginning of the thermal transfer ribbon from damage during installation and shipping.
Trailers are attached to the end of thermal transfer ribbons to signal the end of the ribbon to sensors within the thermal transfer printer and also serve as the point of attachment of the ribbon to the spool on which it is stored.
The materials used for leaders and trailers of thermal transfer ribbons typically are identical to the synthetic resin substrate of the thermal transfer ribbon and so typically are polyethylene terephthalate (PET) polyester films of a thickness greater than the polyester ribbon substrate (about 1 to 1.5 mil) so as to provide greater stiffness. These leaders and trailers can be adhered to the polyester ribbon substrate with conventional pressure sensitive adhesive tape. The trailer can also be attached to the spool upon which the thermal transfer ribbon is stored with conventional pressure sensitive adhesive tape.
One disadvantage of the polyester films used as leaders and trailers is that they do not easily accept print and require complex procedures and printing operations on press to mark them. Therefore, once separated from accompanying materials and packaging, spools of thermal transfer ribbons are difficult to distinguish or identify without marking the spool itself. Due to the limited surface area available for printing on the spool, limited information can be provided. For example, it is not practical to provide instructions and diagrams on threading the thermal transfer ribbon into a thermal transfer printer on the spool. In addition, when a ribbon has been expended, the packaging and materials which accompany the ribbon typically have been disposed of and the operator has little direction with respect to replacement of the ribbon when needed.
The leader and trailer have simple functions and there are many materials which will meet the physical property requirements necessary for the leaders and trailers to perform theses simple functions. For example, U.S. Pat. No. 3,856,228, issued to Hosono et al. on Dec. 24, 1974, describes the use of a leader for magnetic recording tape at column 3, lines 5-8, where the only requirement for the material used is that it have a rigidity high enough to thread through a predetermined passage. Despite their simple functions, the use of materials for the leaders and trailers distinct from the ribbon substrate raises concerns of misalignment with the ribbon substrate, separation due to poor adhesion to the ribbon substrate, stretching during manufacture or use which is mismatched with the ribbon substrate and friction, tension or drag force during manufacture or use which is mismatched with the ribbon substrate. Therefore, using materials for the leader or trailer distinct from the ribbon substrate is generally not preferred and is typically not practiced.
For example, U.S. Pat. No. 4,609,422, issued to Becking on Sep. 2, 1986, describes an apparatus for stuffing pre-inked printer ribbons into a ribbon cartridge wherein the leader is welded to the print ribbon. Such equipment favors the use of similar materials for the leader and print ribbon to provide an effective weld. In addition, where dissimilar materials are used for the leaders and trailers (foil leaders and trailers) for certain typewriters and impact printers, steps are taken to reduce the possibility of misalignment and other problems. In U.S. Pat. No. 4,475,830, Schaefer describes the preparation of print ribbons with foil leaders and trailers without splicing wherein foil composites are laminated directly to the print ribbon substrate. These laminated portions become the leaders and trailers when the ribbon is slit (see column 5, lines 13-20 and 62-63). Since the ribbon substrate is part of the laminate which comprises the leaders and trailers, some of the problems associated with the use of dissimilar materials are avoided.
Uniting bands that accept print have been used in the art of film processing methods, which is non-analogous to the art of print ribbons. In these methods a series of exposed films are attached by uniting bands, referred to as "leaders", to form a continuous web for film processing equipment and methods. U.S. Pat. No. 3,779,837, issued to Zahn et al. on Dec. 18, 1973, discloses the use of an encoding device to apply numbers to the uniting bands and associated envelopes at column 8, lines 47-51. These uniting bands ("leaders") comprise paper and are printed on for purposes of identification. Since the exposed film typically has a paperbacking to shield the film and aid in handling of the film, the use of paper for the uniting bands does not present the problems associated with the use of a material for the leader or trailer distinct from the ribbon substrate. Examples of references which describe the use of printable uniting bands ("leaders") for exposed film are as follows: U.S. Pat. No. 4,432,625, issued to Harvey on Feb. 21, 1984 (see column 3, lines 50-57); and U.S. Pat. No. 3,883,086, issued to Zangenfeind et al. on May 13, 1975 (see column 3, lines 64-68).
Short paper leaders and trailers are described as suitable for film units which contain two polyester films in sheet form in U.S. Pat. No. 5,327,187 (see column 4, lines 31-34). These paper leaders and trailers are attached directly to polyester films without paper backing. The polyester films are part of a complex film laminate and are not in ribbon form consistent with print ribbons.